Battery charging system



Filed April 8, 1929 2 ShetS-Sheet l I *LJ e e( D N Q Q 3 a s s N 9 @AX72/9,94%? 951W? 7726/22/10 (jnventoz @weeg )4). 96a

Oct. 18, 1932. W- BELL 1,883,492

BATTERY CHARGING SYS TEM 2 Sheets-Sheet 2 Filed April 8. 1929 arto: new

Patented Oct. w18, 1.932

PATENT *OFFICE CHART-ES W. BELL, 0F BUFFALO, NEW

I GOULD STORAGE BATTERY CORPORATION,

OF DELAWARE YORK, ASSIGNOR,

BY MESNE ASSIGNMENTS, TO F DEPEW, NEW YORK, .A CORPORATION I BATTERY CHARGING SYSTEM Application filed April 8, 1929. Serial No. 353,585.

The invention relates to charging systems for storage batteries and has for its general object the provision of a circuit arrangement of constant input required to a whereby a variable current is supplied to the battery depending upon its condition, the work it is called upon to do and other circumstances. f

It is well known that there has been a very ystrong trend toward the use of storage batteries on either the floating or trickle charge method of operation. Neither .method has proved entirely satisfactory for various reasons which are mostly as follows: In a pasted plate battery there is a certain minimum rate lead-acid cell (which is not required to do very much work or which does not pass through any considerable portion of a complete cycle of discharge and charge) in order to keep the nega-. tive plates in a live an-d active condition with the lead itself spongy. If this minimum input is not obtained or where the work to be done by the cell is-insufficient to work the negative plates properly, such plates gradual become less and less active, the active material apparentl losing its spongy character and consolidating, thus reducing the activity and capacity. Unfortunately, this minimum currentl required for a ioating battery to keepthe negative plates active is a rate too high for the positive plates and causes quite rapi wear thereon. The operator of such abattery is consequently on the horns of a dilemma.. If a trickle charge rate sufficiently high to keep the ynegative plates active is employed, the positive plates are abused and if the input rate is reduced to a point suitable for the positive plates the negatives being to give trouble on account of losing their spongy characteristics. y

It is with the above facts in View that I have devised the present invention which comprises a circuit so arranged as to perform a certain deiinite cycle-in operation which overcomes the above objections without re- ,lducing the reliability of the installation from' the standpoint of its being maintained in a condition fof charge sufficient to .take care of an4 emergency. My system contemplates the employment of two schemes or,rather one as slowly discharge to a vundue wear or action on a basis with an extension thereof as a modification or alternative.

Broadly considered, the first or basic scheme comprises a circuit arrangedin such manner that assuming we start with a battery in a state of full charge, the battery will given point, say for example sevent-y-ive (7 5) to eighty per cent (80%) charge, subsequently to which the system will operate to put into the battery a rate of charge sufficiently high to maintain theA` negative plates in good condition. rate proper for this purpose will not cause the positive plates because it is put into the battery only when the plates arel below a state of full charge; As soon as an approximately fully charged condition is restored the mechanism will operate to permit the battery to slowly discharge itself back to the minimum selected point, say seventy-live (7 5) to eighty per cent (80%) charged. In this way apparent that the system is, in a Way, a speciesof combination of with a partial cycle though it should be noted that the discharge cycle is only a comparatively small one and is stopped before the battery is discharged to a point which would aiiect the reliability or of an emergencyl condition. The recharge cycle is carried out at a charging rate which while-sufficiently highlto keep the negatives in good condition is not high enough to cause undue wear as would be the case in a battery recharged at the normal rate in a full cycle method of operation. Furthermore, the sequentialpartial charge, discharge and re-A charge will operate to maintain the battery in good condition throughout, as should .be realized by those experienced in storagebattery practice. y

The extension -or alternative of the above described basic scheme is the application of a third element in the 'circuit which comes into operationonly discharged as the result of an emergency to a point somewhat point for the basic scheme. Assuming that the basic, scheme operates at the specified point 'ofseventy-ive (7 5) to eighty per centv it will be.

the trickle charge if the battery becomes below the determining y I (80%) charge,

- charge condition, this then the third element will come into operation at a point approximately sixty-tive (65) to seventy per cent (70%) charge. This third element operates in such manner that if the battery, through an emergency discharge, falls to a point below sixtyfive (65) to seventy-five per cent (75%) charged it will operate to increase the input so that this input will be considerably higher than that on the charge cycle of the basic scheme, probably approximately the normal charge rate of the battery or possibly a still higher rate, the increase continuing only until the battery returns to its determining point of sixty-live (65) to seventy per 'cent barge whereupon the basic condition will be restored. A fairly high rate of charge when the battery is below sixty-five (65) to seventy per cent (70%) charged will not cause undue wear because at a fairly high rate below this point gassing and heating will not occur. At the same time, the reliability of the installation is assured by the rapid return of the ybattery to the sixty-live (65) to seventy per cent charged point in case of emergency discharge.

While it is conceivable that the invention may be carried out in numerous ways, I have illustrated, diagrammatically, how the desired results may be brought about.

In the drawings:

Figure l is a diagram indicating the operating cycle in accordance with the basic scheme,

Figure 2 is a similar diagram indicating theFpperation of the modified system, and

gures 3, 4, 5 and 6 are diagrams showing .R

circuit arrangements for carrying out the invention.

Referring more particularly tothe drawings, Figure 1 discloses the curve for the operating cycle, the percentage of charge being plotted against time. It will be observed that thebattery, starting at a condition `of full charge or one hundred per centr( 100%), slowly discharges itself to a condition of a proximately seventy-five per cent charged in about a twenty-four hour period. It is then returned to a condition ot full charge in a twelve hour period, and this cycle is repeated. The time periods given are not absolute but it is intended that they be worked out for particular sizes and types of batteries and certain applications so that the time `period of the recharge portion of the cycle will bear such relation to the full cycle that the rate of recharge will be sufficient-ly high to maintain the negative plates in good condition and yet low enough to prevent undue wear on the positive plates.

Figure 2 shows the same system amplilied to include an emergency discharge and rebeing indicated by the mar red dip in the curve where the percentage of charge is shown as having dropped from iow into the battery.

eighty-four per cent (84%) tovforty-seven percent (47%) in a very brief time subsequently to which the increased charging rate brings the percentage of charge up to approximately sixty-three per cent (63%) with a more gradual rise thereafter.

Figure discloses an arrangement whereby the diagrammatic action illustrated in Figure l may be accomplished. In this figure,the letter A designates a storage battery across which there is a steady load, the conductor B being in the output circuit and the conductor C representing the input circuit. In a case like this there will be two input rates, one for the slow 4discharge cycle which is suliciently less than the output fromv the battery to cause the battery to discharge slowly. This input rate may conveniently be called X. Secondly, there is to be a higher input rate which is suliciently higher than the steady output load as to cause an appreciable input, enough to keep the negatives in good condition but insuiicient to cause undue wear on the positives providing this higher rate is reduced when the battery reaches the state of approximately full charge. This higher rate may conveniently be designated as Y. In this figure, R1 designates a resistance of such size that when it is the only resistance in the circuit the input rate Y will R2 is an additional resistance which is of such size that when in series with R1 there will be the lower input previously designated as X. designates a mechanism so arranged that when the battery reaches a state of full charge the resistance 2 is cut into the circuit C, and when the battery drops to a condition of seventy-five (75) to eighty per cent (80%) charged R? will be cut out ofthe mechanism. This mechanism S may of course be anything suitable or desirable for the purpose, there being no particular limitation as to the exact form thereof or how it accomplishes the desired action. However, for purposes of illustration only, I have shown this device as comprising a conventional type of relay or electromagnetic circuit controller includinga Solenoid l having a movable core 2 slidable therein and carrying a contact 3 adapted to engage a pair of contacts 4 and 5 connected with one conductor of the charging line at opposite ends of the resistance R2. It is clear that whenthe battery drops to a condition of 75 to charged, the solenoid 1 will be weakened and will permit the core 2 to drop, the contact 3 then bridging the contacts 4 and 5 and shorting out the resistance R2 so that thecharging rate to the battery will be increased.

In Figure 4 I'have illustrated substantially the same application 4in the case of a battery operating on a circuit in which there is n ot a steady load on the battery. In this instance the controlling mechanism operates to result put a small steady discharge load across the battery, as represented by R3, of a size sulficient todischarge the battery slowly and open the input circuit. In this circuit there is provided a mechanism S1 for accomplishing and Ifalso provide a resistance R* correspondingto the resistance R2; For the sake of illustration, the mechanism S1 is shown as comprising a solenoid 6 having` a slidable core 7 and carrying a contact 8 adapted to engage and bridge a pair of contacts 9 and 10, the former of which is connected with one terminal ofthe resistance R3, the other terminal of which is connected with one conductorof the charging line and one battery.

terminal, and the'latter.ofwhich is` connected with the other terminalof the battery. The solenoid also carries a contact 11 adapted-to engage and bridge a pair of contacts 12 and 13 interposed in the other conductor of the charging line. In this instance under normal circumstances the solenoid 6 is not strong enough to draw the core 7 into itself and the is that the contact 1-1 bridges the contacts 12 and 13 for closing the charging circuit. If, however, the battery becomes overcharged or charged vto an extent beyond that 'considered the safest or best, the solenoid 6 which is always connected across the battery will be strengthened and will draw the core 7 upwardly so that the contact 8 will engage and bridge the contacts9 and 10 while at they same time the contact 11 disengages thecontacts 12 and 13. It will therefore be clear l ance R3.

that the charging circuit is broken and the resistance R3 put across the battery for providing an artificial loa'd which will operate to reduce the voltage of the battery until the solenoid is sufiiciently weakenedfthat the core and contacts may againdrop and reclose the charging circuitwhile cutting out the resist- Figure -5 represents the same general scheme amplified to take care of the necessary rapid recharging of the battery in the event that an emergency discharge has occurred. In this instance use is made of a mechanism S2 corresponding to that at S in Figure 3, together with resistanees R5 and RG corresponding to the resistances R1` and R2.

In addition to this there is provided a mechanism T, similar to that at S2, which operates when the battery falls to a point of sixty-five toseventy per cent (70%) charged to 'additionally increasethe rate by cutting out theresistance R7. In thisv connection, the resistaiices R5 and R'I would be equal to the resistance R1 in Figure 3 and would be of sufficient size to increase the input rate to Z which is still greater than the input rate Y above referred to. While the mechanism T may be of any preferred type appropriate for the purpose, itllis here disclosed as comprising 'a solenoidfff14 connected across the PVbattery and having a slidable core 15 carryin a contact 16 adapted to engage and brldge a pair of contacts 17 and 18 connected with the opposite terminals of the resistance R7; Clearly, under normal circumstances the solenoid 1 is sufiiciently strong to hold the core 2 elevated with the Contact 3 out of engagement with the contacts 4 and 5,- the solenoid 14 having also sufficient strength to hold the core 15 up with the contact 16 out of engagement with the contacts 17 and 18,. The windings of the solenoids 1 and 14 are so proportioned or related that they operate in sequence, the strength of the solenoid 1 being decreased when the battery drops to a condition of say to 80% charged so that the Contact 3 will engage and bridge the contacts 4 and 5 for cutting out the resistance R6, while the solenoid 14 still has sufficient strength to holdthe core 15 and contact 16 up until the battery drops to a conditionof say 65 to 70% charged whereupon it will he v sufficiently weakened to .permit the .core 15 and contact 16 to drop and bridge the contacts 17 and 18 for cutting out the resistance R7 and additionally increasing the charging rate. Of course as the battery becomes increasingly charged the strengthening of 'the solenoid14 will operate to break the connection between `the contacts 17 and 18 for throwing the resistance R7 into the charging circuit, subsequentlyto which as the battery approaches the maximum charged condition,- the strengthening of the solenoid 1 will `oper-' ate to draw up the cor-e2 and Contact 3 for breaking the connection between the contact-s 4 and 5 so that the resistance R6 will be cut into the circuit for additionally reducing the charging rate. l

In Figure 6, I have illustrated a condition in which the battery does not have a steady load across it. In this circuit there are provided resistances R3, R9 and R19, the first two corresponding to the resistance R7 in Figure 5 and the lastvmentioned corresponding to R3 in Figure 4. There is also provided a mechanism S3 corresponding to Si, in Figure 4, together with a mechanism -T1 corresponding to the mechanism T in Figure 5. In this instance the total of R8 `and R is equal to R1 in Figure 3 and R11 is of such ,size that when cut out of the circuit the input rate will be of the value Y above referred to, Figure 6 therefore shows a structure combining the actions and advantages of what is shown in Figures 3 and 4 as means is provided Afor providing an artificial load and breaking the input circuit-when the battery stitute no departure from the spirit of the invention or the scope of the claims hereunto appended.

Having thus described the invention, I claim: l

l. The method of operating a storage battery subjected to a variable load comprising applying a predetermined input rate thereto during normal load conditions, automatically increasing the said rate in the event of a sudden discharge while maintaining constant connection with the load and supplyying an artiicial load and discontinuing the storage battery,y

input automatically when the percentcharged-condition exceeds a maximum.

2. In a storage battery charging system, resistances in the input circuit, a circuit closer connected across the battery and operable to cut in additional resistance for reducing the charging rate when the battery approaches a fully charged condition, and a circuit closer connected across the battery for increasing the charging rate when the battery aproaches the minimum desirable charged con- Idition, the input being constantly connected to the battery.

3. In a storage battery system; a storage battery having input and output circuits connected thereto, an artificial load in the outmum per-cent-charged-condition for increas# ing the current in the charging circuit, an

artificial load, and means res onsive to an increase in the per-cent-charge -condition of the battery for connecting the artificial load across the battery and disconnecting the put circuit for discharging the battery at a low rate when the battery voltage exceeds a predetermined limit, and means in the input circuit responsive to the voltage of the attery for recharging the battery when the same has been discharged within a predeter- 4 mined per centcharged condition.

4. In a storage battery system, a storage battery, input and output circuits therefor,

an artificial load adapted to be connected automatically in the output circuit for reducing the per cent-charged condition of the battery to a predetermined point, resistance means in the input circuit, and means responsive to per cent-charged-condition of the battery for cutting successive portions of said resistance. sequentially into or out of the input circuit.`

5. In a storage battery system including a a charging circuit therefor connected therewith and a variable load connected thereto, electro-magnetically operated means responsive to a decrease in the strength of the battery below a predetermined mini- 

